Lean Six Sigma Black Belt Practice Exam — All Questions

Which document formally authorizes a Six Sigma project and defines its scope, goal, and team?

• a.Control plan
• b.Project charter✓
• c.Control chart
• d.Gage R&R report

The project charter authorizes the project and defines scope, goals, and roles.

A SIPOC diagram maps:

• a.Suppliers, Inputs, Process, Outputs, and Customers✓
• b.Only defects
• c.Only costs
• d.Only control limits

SIPOC gives a high-level view of Suppliers, Inputs, Process, Outputs, and Customers.

'Voice of the Customer' (VOC) is used primarily to:

• a.Set the control limits
• b.Compute DPMO
• c.Identify Critical-to-Quality (CTQ) requirements✓
• d.Run a hypothesis test

VOC is translated into measurable CTQ requirements.

A Black Belt's role typically includes:

• a.Only data entry
• b.Approving budgets only
• c.Auditing finances
• d.Leading projects and mentoring Green Belts✓

Black Belts lead improvement projects and coach Green Belts.

A process produces 15 defects across 300 units, each with 5 defect opportunities. What is the DPMO?

• a.5,000
• b.10,000✓
• c.1,500
• d.50,000

DPMO = 15 / (300 x 5) x 1,000,000 = 15/1500 x 1,000,000 = 10,000.

Approximately how many DPMO corresponds to a 3-sigma process (with the 1.5-sigma shift)?

• a.About 66,807✓
• b.About 3.4
• c.About 233
• d.About 6,210

A 3-sigma process is roughly 66,807 DPMO; 6 sigma is 3.4 DPMO.

Gage R&R (a Measurement System Analysis) assesses:

• a.Customer satisfaction
• b.Project ROI
• c.Repeatability and reproducibility of the measurement system✓
• d.The control plan

Gage R&R quantifies measurement variation from equipment (repeatability) and appraisers (reproducibility).

A process has USL 110, LSL 90, and a standard deviation of 2.5 (centered). What is Cp?

• a.1.00
• b.2.00
• c.0.67
• d.1.33✓

Cp = (USL - LSL) / (6 x sigma) = 20 / 15 = 1.33.

In hypothesis testing, if the p-value is 0.03 and alpha is 0.05, you should:

• a.Fail to reject the null hypothesis
• b.Reject the null hypothesis✓
• c.Increase the sample to 1,000 first
• d.Do nothing; p-values are irrelevant

Because p (0.03) < alpha (0.05), you reject the null hypothesis.

A Type I error occurs when you:

• a.Reject a true null hypothesis (a false positive)✓
• b.Accept a true null hypothesis
• c.Increase the sample size
• d.Compute DPMO incorrectly

A Type I (alpha) error is rejecting a null hypothesis that is actually true.

A correlation coefficient (r) of -0.9 indicates:

• a.No relationship
• b.A weak positive relationship
• c.A strong negative linear relationship✓
• d.A guaranteed causal link

r = -0.9 indicates a strong negative linear correlation (correlation is not causation).

Which tool helps prioritize the 'vital few' causes contributing most to a problem?

• a.Control chart
• b.Gage R&R
• c.SIPOC
• d.Pareto chart✓

A Pareto chart highlights the vital few causes (the 80/20 principle).

Design of Experiments (DOE) is used to:

• a.Monitor a stable process
• b.Systematically study the effect of multiple factors and their interactions✓
• c.Write the project charter
• d.Compute the p-value only

DOE varies factors deliberately to identify significant effects and interactions.

A key advantage of a factorial DOE over changing one factor at a time is that it can:

• a.Detect interactions between factors✓
• b.Avoid all measurement
• c.Eliminate the need for data
• d.Guarantee zero defects

Factorial designs reveal interactions that one-factor-at-a-time testing misses.

A pilot of an improvement is run before full rollout mainly to:

• a.Replace the control plan
• b.Skip the Control phase
• c.Validate the solution and reduce risk before scaling✓
• d.Set the USL and LSL

Piloting validates the improvement and reduces risk before full implementation.

Poka-yoke (mistake-proofing) aims to:

• a.Increase inspection staff
• b.Widen the specification limits
• c.Add more defects for testing
• d.Prevent errors from occurring or being passed on✓

Poka-yoke prevents defects at the source or stops them from moving downstream.

On a control chart, a single point beyond the upper control limit indicates:

• a.Common-cause variation
• b.A special (assignable) cause to investigate✓
• c.That the spec limits are wrong
• d.That DPMO is zero

A point beyond the control limits signals special-cause variation to investigate.

Control limits on a control chart are:

• a.Calculated from the process data (typically ±3 sigma)✓
• b.The same as the customer specification limits
• c.Set by the customer
• d.Always ±1 sigma

Control limits are derived from process variation (commonly ±3 sigma), distinct from spec limits.

The main purpose of a control plan in the Control phase is to:

• a.Define the project charter
• b.Run a DOE
• c.Document how to monitor and sustain the improved process✓
• d.Compute Cp

A control plan documents monitoring and response to sustain the gains.

Statistical Process Control (SPC) primarily helps distinguish:

• a.Suppliers from customers
• b.Costs from benefits
• c.Inputs from outputs
• d.Common-cause from special-cause variation✓

SPC separates normal common-cause variation from special-cause variation.